Manipulating CSS classes with the JavaScript classList API

In the world of web development, JavaScript is one of the most used languages to add dynamism and interactivity to pages. One of the most important aspects of frontend development is the manipulation of CSS classes, and in this article we will focus on how to do it using the JavaScript classList API.

What is the JavaScript classList API?

The classList API is an interface provided by JavaScript that allows us to manipulate the CSS classes of an element in the DOM in a much simpler and more efficient way than using traditional methods such as element.className.

The classList API gives us four key methods:

• add(): to add a class to an element.
• remove(): to remove a class from an element.
• toggle(): to add or remove a class from an element, depending on whether it is present or not.
• contains(): to check if an element has a specific class.

Manipulating CSS classes with the classList API

To use the classList API, we must first select the element in the DOM whose classes we want to manipulate. This can be done using methods like querySelector() o getElementById().

const element = document.querySelector('.my-item');

Next, we can use the classList API methods to add, remove, toggle, or check classes on the selected element.

// Add a class element.classList.add('new-class'); // Remove a class element.classList.remove('class-to-remove'); // Toggle a class element.classList.toggle('class-to-toggle'); // Check if it has a class if (element.classList.contains('class-to-check')) { // Perform some action }

In addition to these four methods, the classList API also allows us to access the complete list of classes of an element through the property classList.

// Get the list of classes const classes = element.classList; console.log(classes); // ["class1", "class2", "class3"]

Benefits of using the JavaScript classList API

The classList API offers us a more efficient and simple way to manipulate the CSS classes of an element in the DOM. By using this API, we avoid having to work directly with the text string that represents the element classes, which can be error-prone and difficult to maintain the code.

Additionally, the classList API also provides us with additional methods like replace() y item() that allow us to replace an existing class with another, as well as access a particular class from the complete list of classes.

Conclusion

Manipulating CSS classes is a fundamental part of web development, and thanks to the JavaScript classList API, we can use more efficient and simple methods to accomplish this task. Whether adding, removing, toggling or verifying classes in an element, the classList API provides us with the necessary tools to achieve this.

I hope this article has been useful to you and that you can apply this knowledge in your projects. If you have any questions or comments, feel free to contact me through my blog at nelkodev.com. I'll be happy to help you.

Frequently asked questions

1. What is the difference between using classList and className in JavaScript?

   classList is a more modern and efficient API than className. While className only allows access to the classes of an element as a text string, classList allows us to use specific methods to add, remove, toggle and verify classes more easily.

2. Can I use the classList API in older browsers?

   Yes, the classList API is supported by most modern browsers, including older versions of Internet Explorer. However, if you need compatibility with older browsers, you can use polyfills or libraries like classList.js that simulate the behavior of the API.

3. Can I manipulate the classes of multiple elements at once using the classList API?

   Yes, you can use methods like forEach() o querySelectorAll() to select multiple elements and then manipulate their classes using JavaScript's classList API.